Particles with several different functions are sometimes called Janus-particles, named after the Roman god Janus. Janus-particles can be considered a sub-group of the collective term “dis-symmetrical particles”, which also includes particles differing in shape and bulk content. Such particles have been studied previously, for instance Zhang et al. patterned 270 and 925 nm polystyrene particles by spreading them in a mono-layer onto a surface, masking them with a mono- or bi-layer of silica particles on top and finally evaporating gold onto the bi- or tri-layer. The bottom layer of polystyrene particles became surface-patterned of gold depending on the packing-pattern of silica-particles on top (G. Zhang et al, Nano Letters 5, No 1 (2005), 143-146). In a continued study by the same group particles with multiple dots (2-5) in symmetric patterns were obtained by increasing the number of particle-layers in combination with reducing the size of the uppermost particles (G. Zhang et al, Angewandte Chemie Int E. 44 (2005), 7767-7770). A micro-contact printing technique has been used to synthesize latex particles with dipolar properties. The principle is to spread the particles on a glass slide and have a coating on a PDMS-stamp, which is then pressed against the glass slide. In the first work, negatively charged polystyrene particles were asymmetrically (hemispherical) coated with a cationic surfactant, which bound hydrophobically to the particles, thus making a particle with two opposing charges (O. Cayre et al, Chem Commun, 2003, 2296-2297). In the second work, they used the same method to stamp a layer of 1.5 μm sulphate-coated particles on a hemisphere of 10 μm amine-coated particles (O. Cayre et al, 2003, 2445-2450). Nie et al. synthesized bi- and tri-functional (dis-symmetrical) particles by polymerization of droplets of two or three monomers flowing parallel in streams which passed through a nozzle, making the droplets. The particles produced in this manner were sized 40-100 μm and had a dis-symmetric distribution of the monomers within the particles (Z. Nie et al, 2006, JACS 128, 9408-9412). Matsunaga et al. presented the concept “particles-on-particles”, where bacterial magnetic nano-particles (50-100 nm diameter) were bound to the surface of non-magnetic polystyrene particles (6 μm diameter). The surface of the polystyrene particles was coated with streptavidin, which selectively binds to biotin. The surface of the nano-particles was coated partly with biotin, partly with the IgG-binding part of protein A. This system is thus capable of binding IgG from a solution onto nano-particles that are further bound to the surface of particles, which then become magnetic. According to Matsunaga et al, with this strategy it is possible to increase the effective surface area and thus increase the amount of protein bound to a micro-particle by taking advantage of the larger surface/volume ratio of the nano-particles as compared to a micro-particle and at the same time take advantage of the lesser tendency of micro-particles to aggregate and stick onto e.g. pipette surfaces as compared to nano-particles (Matsunaga et al, Analytica Chimica Acta 597 (2007), 337-339). Pregibon et al presented a lithographic method to continuously fabricate and encode dis-symmetrical polymeric particles from a monomer flow in a one-step process. The particles comprised two parts: one encoding part which identified the particle and one probing part to which an analyte could bind. In the simplest case, two parallel laminar flows containing the two monomers were streaming through a channel, in which the monomers were exposed to a UV-burst that induced polymerization at the exposed area. The UV light was passed through an optical mask, which defined the encoding pattern on the particle as well as the particle shape. The stream of monomer which makes up the probing part of the particle also contain the probe, and thus the probing part of the synthesized particles can be directly identified by the written pattern. The particles were mixed with a sample containing fluorescence labeled DNA oligomers, and subsequently passed through a reading device, which identified the pattern on the particle and the presence or absence of fluorescence on the probing part (Pregibon at al., Science 315 (2007) 1393-1396.
Pavlovic et al. used electro contact printing to immobilize proteins in patterns on a thiolated flat silicon surface, by site-selective oxidation of thiols to thiolsulphinates (Nanoletters vol. 3, No. 6, 779-781, 2003).
It is known to modify planar surfaces with thiol groups, where an electrical potential is applied between the planar surface and an electrode close to the surface. As a result thiosulfinate/thiosulfonate groups are formed on the surface. The thiosulfinate/thiosulfonate groups on the planar surface can later be reacted with thiol groups to form covalent bonds.
There is a need of miniaturization of components within nanotechnology, diagnosis, research and development. Within many areas there is a need to store information or attach various molecules on a particle. If it is possible to manufacture particles with a partially derivatized surface, this will open a lot of possible uses.
There are known technologies to store information on larger particles and to derivatize large particles. Regarding partial derivatization of smaller particles, such as particles with a diameter below 100 μm, technical problems arise. One problem is the control of the particle movement. Thus there is a need in the art for a method to manufacture partially derivatized smaller particles.